This invention relates to an optical disk manufacturing method, and more particularly to a method of connecting a clamping plate to the center of a disk body. In this patent application, the term optical disk is used in the broader context to include optical-magnetic disks.
The optical disk has a clamping plate fixed at its center. The clamping plate allows rotation of the disk, and a sheet metal stamped into a disk shape is used as the clamping plate. The clamping plate is connected to the body of the disk at its center. In the case of a mini-disk (MD), the clamping plate is not fixed to the body of the disk, but is joined to it in a fashion allowing some play.
FIG. 1 and FIG. 2 show a prior art method of joining a clamping plate to the body of a disk. FIG. 1 shows the clamping plate 2 set in position in a cavity 1A provided at the center of the disk body 1. FIG. 2 shows the clamping plate 2 joined to the disk body 1 by compression around the perimeter of the cavity 1A with a heat press 5. This method of connecting the clamping plate has the feature that the clamping plate can be efficiently connected to the disk without the use of adhesive bond or an adhesive tape.
However as shown in FIG. 2, connecting the clamping plate by this method has the drawback that a protrusion 6 is created outside the perimeter compressed by the heat press 5. The protrusion 6 projects above the plane of the surface of the disk body 1 and has a detrimental effect on the operation of an optical disk drive. For example, when a drive head, which is extremely close to the surface of the disk, moves over this region it may be damaged by contact with the protrusion. Further, since the protrusion is not uniform around the entire perimeter but rather has regions with different heights, aerodynamic .drag is increased adding a significant load to the driving motor. Ideally, the surface of an optical disk joined with a clamping plate should be planar with no protrusions.
This invention was developed to achieve this goal, and it is thus a primary object of the present invention to provide an optical disk manufacturing method that can join the clamping plate and prevent creation of a protrusion out of the plane of the disk surface.
The above and further objects and features of the invention will more fully be apparent from the following detailed description and the accompanying drawings.